DETROIT— Lexus has a full lineup of hybrids—four at last count—including the RX450h we recently test drove. Yet none thus far has been built from the beginning, solely as a hybrid. Well, this summer, that will change.

The Lexus HS250h rides on a front-drive platform not shared with any other Lexus or Toyota in the U.S. However, Lexus insiders say that it does share many components with the European Toyota Avensis sedan. The bodywork has been optimized for aerodynamic performance to help boost highway fuel economy and it results in a 0.27 drag coefficient. In terms of size, the HS250h falls right in between the Lexus IS and ES sedans and rides on 215/55R17 or optional 225/45R18 tires.

This new Lexus hybrid borrows its drivetrain largely from the current Camry Hybrid, and that includes the 2.4-liter Atkinson-cycle four-cylinder, electric motor and the battery pack too. In the Lexus, the system in totality produces 187 hp.

The HS250h, like the RX450h, has a new exhaust-heat gas recovery system for improved efficiency. The system reduces engine warm-up times, allowing the engine stop/start system to kick in sooner, more often and for longer times. Fuel-economy numbers have not been released but since the Camry Hybrid returns 34 mpg combined, we expect this Lexus will return numbers close to the high thirties.

Inside, the HS250h looks like it was inspired a bit by the Toyota Prius. In other words, it will probably feel like you are driving a hybrid—not just a sedan converted to "hybrid." Many of the interior parts will be composed of what the company is calling plant-based "ecological plastics"—whether that means it's low-energy manufacturing, biodegradable materials, or something else is still in the air. The new Remote Touch haptic controller we like so much in the new RX is available in the HS250h, too. And because it's a Lexus, there'll be a long list of luxury features including a new wide-view front-monitor system—to produce a 190-degree front view on the nav screen at the push of the steering-wheel-mounted button. —Ben Stewart

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